In accordance with development of device technology, research for an high-integrated circuit (IC) have been actively performed as one strategic product distinctive from CMOS image sensor (CIS). Using a semiconductor manufacturing method, a color filter and a micro lens are formed at an upper part of a photodiode. On the other hand, using a high IC manufacturing method which is under active research, a photodiode is formed on and/or over a bare Si wafer by H2 ion implantation and the photodiode is then bonded to a pattern wafer. Here, tungsten (W) may be used to connect those two wafers. To accomplish this, via holes are formed in the respective wafers, having a minimum width of about 10 μm and a minimum depth of about 70 μm. Such a small size of the via holes causes difficulty in thorough removal of residues remaining in the via holes. Although etching may be performed to produce a via plug and then a native oxide is removed using an HF-based etchant, a process removing residues as a byproduct is not widely known. In addition, since a Ti/TiN layer used as a barrier metal also needs to be removed in addition to the W, it becomes complicated to set up the process for bonding the two wafers so that the W, Ti and TiN layers are removed simultaneously up to the bonding portion. Meaning, the necessity for simultaneously and selectively processing the W, Ti and TiN layers is currently growing.